High-speed optical modulators are desirable for a variety of telecommunications applications. Ring resonators are often desirable modulators due to their low power consumption, small sizes, and fast modulation speeds. These modulators have a loop waveguide optically coupled with a bus (input/output) waveguide. The modulator includes a phase modulator that phase modulates a light signal in the ring resonator. This phase modulation changes the phase difference between the light signal in the loop waveguide and the light signal in the bus waveguide. The phase difference can be controlled so as to create constructive interference between the light signal in the loop waveguide and the light signal in the bus waveguide. When constructive interference is achieved, the intensity of the light signal output from the bus waveguide decreases from the intensity that results when constructive interference is not achieved. As a result, the phase modulation of the light signal in the loop waveguide can be used to intensity modulate the output from the loop waveguide.
The band of wavelengths that can be effectively intensity modulated by the phase modulator is the phase modulator bandwidth for the ring resonator. The phase modulator bandwidth is undesirably low for most practical applications. As a result, some ring resonators include temperature control devices that can be employed to tune the bandwidth of the ring resonator. This tuning generally shifts the wavelengths that fall within the bandwidth but does not substantially increase or decrease the range of wavelengths that fall within the phase modulator bandwidth. However, the range of this bandwidth shift is often undesirably low. As a result, the total range of wavelengths that can be modulated by ring resonators is often undesirably low. For these reasons, there is a desire to increase the range of wavelengths that can be modulated by ring a resonator.